1. Field of the Invention
This invention relates to improvements in well bore drilling method and means and more particularly, but not by way of limitation, to a well bore drilling method and means whereby oxygen content of well drilling muds is replaced by nitrogen, exhaust gases, or gaseous mixtures of combustible products for reduction of corrosion.
2. Description of the Prior Art
In the drilling of an oil or gas well, the drilling operation normally comprises the piercing of the earth by means of a drill bit carried at the lower end of a string of drill pipe. The drill bit penetrates the earth to create the well bore, and the drill string is continually lengthened during the drilling process as the bit cuts or drills deeper into the earth.
One drilling method in widespread use today utilizes a drilling fluid for facilitating the drilling operation performed by the drill bit. The drilling fluid is usually circulated downwardly through the drill pipe to the drill bit for flushing or washing away cuttings and other debris from the bottom of the well bore which might hinder the operation of the bit. The drilling fluid and cuttings and/or particles is then pumped upwardly in the well bore through the annulus between the outer periphery of the drill pipe and the walls of the well bore and to the surface of the earth where the drilling fluid is directed into the mud pits normally provided in the proximity of the well bore for storage of the fluid in order that the fluids may be reused. The mud pits are normally open storage pits, and the fluid retained therein is frequently contaminated by the oxygen present in the atmosphere adjacent the exposed upper surface of the stored mud. In addition, oxygen may contaminate the drilling fluids during mixing thereof and during removal of cuttings and the like from the circulated fluids. Of course, oxygen in the drilling fluids is a great disadvantage in that the circulation of the fluids in the well bore brings the drilling fluid into intimate contact with substantially the entire inner and outer peripheries of the drill pipe as well as the drill bit, and the oxygen in the drilling fluids causes corrosion of any metallic equipment with which it is in contact. Because of the current use of polymer-type drilling fluids utilizing the salts of sodium and potassium, the problem of corrosion is greatly increased in the presence of oxygen, making it more necessary than ever to reduce or eliminate the oxygen content of the drilling fluids.
Various chemicals are frequently used to react with and remove the dissolved or entrained oxygen in the drilling fluids and are somewhat effective in the alleviation of the corrosive condition that occurs, especially on the inner periphery of the drill pipe. However, any oxygen contained in the drilling fluid is a disadvantage, and any corrosion of the drill pipe is extremely disadvantageous, particularly in the light of the present-day costs and scarcity of materials.
There is also increasing demand for delivery of coal and the like through pipelines, and movement of materials in this manner requires a slurry in combination with the materials for passing thereof through the pipeline. Water is normally used in the slurry, and the oxygen content of the slurry increases the corrosion problem of the inner periphery of the pipe.